High-speed Scanning Tunneling Microscope Research Articles

A high-speed variable-temperature ultrahigh vacuum scanning tunneling microscope with spiral scan capabilities.

We present the design and development of a variable-temperature high-speed scanning tunneling microscope (STM). The setup consists of a two-chamber ultra-high vacuum system, including a preparation and a main chamber. The preparation chamber is equipped with standard preparation tools for sample cleaning and film growth. The main chamber hosts the STM that is located within a continuous flow cryostat for counter-cooling during high-temperature measurements. The microscope body is compact, rigid, and highly symmetric to ensure vibrational stability and low thermal drift. We designed a hybrid scanner made of two independent tube piezos for slow and fast scanning, respectively. A commercial STM controller is used for slow scanning, while a high-speed Versa Module Eurocard bus system controls fast scanning. Here, we implement non-conventional spiral geometries for high-speed scanning, which consist of smooth sine and cosine signals created by an arbitrary waveform generator. The tip scans in a quasi-constant height mode, where the logarithm of the tunneling current signal can be regarded as roughly proportional to the surface topography. Scan control and data acquisition have been programmed in the experimental physics and industrial control system framework. With the spiral scans, we atomically resolved diffusion processes of oxygen atoms on the Ru(0001) surface and achieved a time resolution of 8.3 ms per frame at different temperatures. Variable-temperature measurements reveal an influence of the temperature on the oxygen diffusion rate.

100 MHz large bandwidth preamplifier and record-breaking 50 kHz scanning rate quantum point contact mode probe microscopy imaging with atomic resolution.

The high-bandwidth preamplifier is a vital component designed to increase the scanning speed of a high-speed scanning tunneling microscope (STM). However, the bandwidth is limited not only by the characteristic GΩ feedback resistor RF but also by the characteristic unity-gain-stable operational amplifier (UGS-OPA) in the STM preamplifier. Here, we report that paralleling a resistor with the tunneling junction (PRTJ) can break both limitations. Then, the UGS-OPA can be replaced by a higher rate, higher antinoise ability, decompensated OPA. By doing so, a bandwidth of more than 100 MHz was achieved in the STM preamplifier with decompensated OPA657, and a higher bandwidth is possible. High-clarity atomic resolution STM images were obtained under about 10 MHz bandwidth and quantum point contact microscopy mode with a record-breaking line rate of 50 k lines/s and a record-breaking frame rate of 250 frames/s. Both the PRTJ method and the decompensated OPA will pave the way for higher scanning speeds and play a key role in the design of high-performance STMs.

Watching graphene grow

Surface Chemistry The growth of graphene on metal surfaces can be catalyzed by mobile surface metal atoms. Patera et al. used a high-speed scanning tunneling microscope to image the growth of graphene islands on a nickel surface. High temperatures caused carbon to diffuse to the surface, where

An ultrahigh vacuum high speed scanning tunneling microscope

We have developed an ultrahigh vacuum high speed scanning tunneling microscope (STM) which is based on a prototype STM that operates in air. The prototype operates with a tip scan speed up to 105 nm/s. At this high tip speed, we have made real time videos of nickel and gold at rates up to 15 Hz. The ultrahigh vacuum version operates at speeds up to 8000 nm/s with atomic resolution on the Si(111) surface and incorporates sample transfer and sample heating.

Surface energetics and thermal roughening of Ag(115) studied with STM movies

We present a high-speed scanning tunneling microscope ~STM! study of the energetics and the thermal roughening transition of the Ag~115! surface. Using a statistical analysis of large numbers of STM images we directly determine the kink creation energy and the step interaction energy. From these two energies we predict the roughening temperature after the terrace-ledge-kink model of Villain et al. This prediction is compared with an experimental estimate of the roughening temperature, obtained from STM observations at elevated temperatures. In addition, we derive an interaction energy for two neighboring kinks. @S0163-1829~96!50220-1#

Design and performance of a high-temperature, high-speed scanning tunneling microscope

This article describes the design and performance of a new scanning tunneling microscope (STM) which operates at elevated temperatures and high scanning speeds. To minimize the thermal displacements within the STM, a symmetric configuration was chosen with a large temperature gradient between the sample and the piezoelectric scanner. The thermal behavior of the STM was optimized further by means of a finite element analysis. The high scan rates (105 data points/s) are accomplished with fast analogue electronics and a combination of a workstation and three transputers. The STM has imaged surfaces with atomic resolution between room temperature and 750 K, with low residual drifts only two hours after a major temperature change. The sample surface remains within the vertical range of the piezo actuator over a temperature interval of 159 K.

Step dynamics on Au(110) studied with a high-temperature, high-speed scanning tunneling microscope.

The dynamics of monoatomic steps on the Au(110) surface was studied with a scanning tunneling microscope from room temperature to 590 K. The time dependence of the position fluctuations of steps was measured as a function of temperature and kink density. The mean-square displacement of the position was found to be proportional to the square root of time. The proportionality constant exhibits Arrhenius behavior and varies linearly with the kink density. The step dynamics is dominated by the diffusion of geometrical kinks that cannot pass each other